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  <title>Returns the size of the IV of the opened algorithm</title>

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  <h1 class="refname">mcrypt_enc_get_iv_size</h1>
  <p class="verinfo">(PHP 4 &gt;= 4.0.2, PHP 5)</p><p class="refpurpose"><span class="refname">mcrypt_enc_get_iv_size</span> &mdash; <span class="dc-title">Returns the size of the IV of the opened algorithm</span></p>

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 <div class="refsect1 description" id="refsect1-function.mcrypt-enc-get-iv-size-description">
  <h3 class="title">说明</h3>
  <div class="methodsynopsis dc-description">
   <span class="type">int</span> <span class="methodname"><strong>mcrypt_enc_get_iv_size</strong></span>
    ( <span class="methodparam"><span class="type">resource</span> <code class="parameter">$td</code></span>
   )</div>

  <p class="para rdfs-comment">
   This function returns the size of the IV of the algorithm specified by the
   encryption descriptor in bytes. An IV is used in cbc, cfb and ofb modes,
   and in some algorithms in stream mode.
  </p>
 </div>

 <div class="refsect1 parameters" id="refsect1-function.mcrypt-enc-get-iv-size-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>

    
     <dt>
<em><code class="parameter">td</code></em></dt>

     <dd>

      <p class="para">
       The encryption descriptor.
      </p>
     </dd>

    
   </dl>

  </p>
 </div>

 <div class="refsect1 returnvalues" id="refsect1-function.mcrypt-enc-get-iv-size-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   Returns the size of the IV, or 0 if the IV is ignored by the algorithm.
  </p>
 </div>

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